Mine roof bolt installation



April 8, 1958 1 B DEMPSEY 2,829,502

MINE ROOF' BOLT INSTALLATION Filed Dec. 1'7, 1953 INVENTOR Josey/n B .e Ils'ey lll A| Unite States This` invention relates to mine roof lbolts, and more particularly to an improved installation thereof.

Mine roof bolts, and their usages, are known in the art and usually comprise a headed bolt of from about three to about five feet long and an expansible anchoring means threadedly engaged therewith. in use, a mine roof boit is inserted in a drilled hole in a mine roof, with the anchoring means at the inner end of the hole and a large washer seated against the head of the bolt and abutting against the ceiling of the mine. Thereupon, the anchoring means is actuated to expand into tight gripping engagement with the side walls of the hole, and the bolt is placed under tension between the Washer and the anchoring means. The installation of mine roof bolts in this manner in a plurality of holes in a mine roof serves to lock the roof strata together to prevent falling. Thus, mine roof bolts eliminate the timber shoring previously used to support the roofs of passageways and rooms in a mine.

in some instances, however, mine roof strata is somewhat soft and on exposure to air eventually will Slough oif, crumble, or spa-ll, thus permitting a mine roof bolt to fall out of the hole by failure of the formation about the bolt-anchoring means. In this type of roof strata, mine roof bolts heretofore have provided only a temporary support for the roof, the effectiveness of which decreased with passage of time. Accordingly, in the aforedescribed type of mine roof formation, mine roof bolt installations not embodying this invention can be used only where the passageway or room is not a permanent part of the mine labyrinth. Even so, however, the installation of mine roof bolts not embodying this invention is undesirable in strata which tends to eventually crumble or spall because of exposure to air. Because of its weight, a falling mine roof bolt can be quite dangerous to human life. Additionally, the gradual lessening of the supporting eifectiveness of a mine roof bolt tends to create a somewhat dangerous situation.

Accordingly, it is an object of this invention to provide a mine root` bolt installation that is permanently effective, even though the roof strata is of the type that tends to spall or crumble on exposure to air.

It is another object of this invention to provide an irnproved method of installing mine roof bolts to permanently anchor the ibolt in place, even though the roof strata is of a type that crumbles or spalls on exposure to air.

It is a further object of this invention to provide novel apparatus for accomplishing the foregoing objects.

Other objects and: advantages of the invention will become apparent from the following description and accompanying drawings, in which:

Figure l is a Vertical sectional View of a drilled hole in a mine roof showing a mine roof bolt inserted therein for installation in accordance with this invention.

Figure 2 is a horizontal sectional view taken on line 2-2 of Figure 1.

Figure 3 is a horizontal sectional View taken on line 3--3 of Figure l.

arent r1ice Figure 4 is a perspective view of apparatus for installing a mine roof bolt in accordance with this invention.

Figure 5 is a fragmentary view corresponding to Figure l and illustrating a modilied form of apparatus for installing a mine roof bolt in accordance with this invention.

Figure 6 is a fragmentary perspective View of the modied installation apparatus shown in Figure .5.

Referring now to Figure l of the drawings, there is shown therein a hole 10 which has been drilled upwardly from the ceiling 12 of a mine room or passageway into the roof strata 14 thereabove. Positioned in the hole lltl is a mine roof bolt assembly including a bolt lo and an anchoring means 18 of a type disclosed in Dempsey Patent No. 2,753,750, issued July l0, 1956, and to which reference is made for amore detailed description of the anchoring means. The anchoring means liti, which normally is cylindrical and of a diameter slightly less than that of the hole lli, includes a two-part expansible anchoring shell liti and a wedge-shaped nut 22 for expanding the shell.

The shell 20, which normally is generally circular in transverse section and of a diameter only slightly less than that of the drilled hole l0, has two diametrically-opposed parts 24, each part being formed as a longitudinal-tapering segment of a cylinder. The tapering longitudinal plane edges 26 of each part 24 are disposed in a common plane with the edge planes of both parts being upwardly divergent. The smaller and upper ends of the two parts 24 forming the shell 20 are connected together by a springsteel band-like connecting member 28 that is; substantially U-shaped. The connecting member 28 has legs 3d which normally are generally parallel and extend generally longitudinally of the shell 20 and a base 32 which extends transversely of the shell somewhat above the upper ends ol' the two shell parts 24. The two legs Sil of the connecting member 23 may be secured to the shell parts 24 in any appropriate manner, but, as shown, tit into recesses 34 therein and are connected thereto by pins 36 integral with the parts 24, the pins being peened to retain the legs 30 thereon. The curved outer surfaces of the shell parts 24 preferably are provided with a plurality of step-like circumferential sei-rations 38 and vertical serrations (not shown) for embedding and gripping engagement with the side Walls of the hole 10, as later explained. Preferably, the bottom edge 40 of each shell part 24 is sharp, for a reason that will become apparent later.

The nut 22 is disposed between the two parts 24 of the shell 20 and has opposite plane wedging surfaces 42 complementary to, `and in mutually-wedging engagement with, each pair of opposed side plane edges 26 of the shell parts. Preferably, the wedging surfaces 42 on the nut 22 are longer than the longitudinal side edges 26 of the shell parts 24 and extend above the two shell parts, so that when the shell 20 is expanded by downward movement of the nut 22 relative thereto, as later explained, the entire length of the wedging surfaces or plane edges 26 of the two shell parts is engaged with the wedging surfaces on the nut. The exterior surfaces of the nut 22, between its wedging surfaces 42, are arcuate in transverse section, as shown in Figures 2 and 3, to correspond to the circular peripheral outline of the shell 26. At its larger end, the nut 22 is provided with diametric longitudinal channels or grooves 44 to accommodate the legs 30 of the connecting member 28.

The shank 46 of the bolt 16 is threaded into the nut 22, from the lower end thereof, and the lower or outer ment with the ceiling 12 about the hole 10.` The inner diameter of the washer 54 preferably is slightly larger than the diameter of the anchoring means 18 when the latter is unexpanded, so that the washer can pass thereover into engagement with the flange h on the bolt head 48 without disassembly of the bolt 16 from the nut 22.

In use, the mine roof bolt assembly, with the Washer 54 in place thereon, is inserted upwardly into the drilled hole until the washer engages the ceiling 12. In so doing, the upper end of the nut 22 will abut against the underside of the base 32 of the member 28, connecting the shell parts 24, to carry the latter along with the bolt and nut as the assembly is pushed upwardly into the hole 10. Prior to such insertion, the two shell parts 24 are sprung somewhat apart, so that as the assembly is pushed upwardly into the hole 10, the sharp bottom edges 40 of the shell part-s drag against and engage the sides of the hole and retain the assembly therewithin after insertion thereinto. After the assembly has been thus inserted to its full length, the bolt 16 is pulled down somewhat, to thus force the W-edging surfaces 42 of the nut 22 into expanding wedging engagement with the shell parts 24 to force the latter oppositely apart into gripping engagement with the side walls of the hole 10. The bolt 16 is then rotated, as by an appropriate wrench (not shown) `applied to the non-circular portion 52 of the bolt head 48, to thereby draw the washer 54 upwardly into engagement with the ceiling 12 and thereafter draw the nut 22 downwardly into greater wedging engagement with the two shell parts 24 and force the latter in opposite directions into firmer gripping engagement with the sidewalls of the hole. The foregoing steps are the conventional method of installing a mine roof bolt of the type shown in the aforementioned patent. It will readily be seen, however, that the side walls of the hole 10 about the anchoring means 18 are exposed to air, and in the event that the roof strata 14 is of the type that will eventually crumble or spall upon such air exposure, such crumbling or spalling about the anchoring means will eventually relieve its grip upon the side walls of the hole and permit the entire roof bolt assembly to fall out of the same.

In order to obviate the foregoing difficulty, an installation in accordance with this invention seals o the strata 14 engaged by and immediately above and below the anchoring means 18 from access to air. An installation embodying this invention also excludes air from the hole once the assembly is installed therein. Hence, a mine roof bolt installation embodying this invention is substantially permanent.

The improved installation is accomplished by applying and conning a flowable plastic or liquid settable or hardenable cementitious material around and about the nut 22 and the expansible shell 20 when the anchoring mean-s is in place in the hole 10. Materials suitable for this purpose may include cement grout, a water-insoluble glue, an air-hardenable synthetic resin, such as Epon, etc. Preferably, the material is insoluble in water because mine roof starta frequently is damp. In order to apply the material properly, the same preferably is -enclosed within a thin-walled capsule 56 of appropriate material, such as paper which has been treated to render it impervious to the material, a rubber-like material, a synthetic plastic, or the like. This capsule S6 is pushed into the hole 10 ahead of and by the mine roof bolt assembly. In order to avoid rupturing the capsule 56 dur- 4ing its insertion by snagging on the side walls of the hole 10, the capsule preferably i-s enclosed in a reinforcing tube 58, of cardboard or the like, having an open lower end. The lower edge of the tube 58 preferably is provided with an inturned small flange or bead 60 for retaining the capsule 56 therewithin and for engagement by the roof bolt assembly to further avoid possible rupture of the capsule during its insertion. In this connection, the base 32 of the connecting member 28 preferably is provided with lateral extensions 62, as shown in Figure 3, to provide more than two areas of engagement with the capsule-enclosing tube 58. Also, in order to avoid possible snagging of the tube 58 on the side wall of the hole 10 during its insertion, the upper end of the tube is tapered or of ogival shape as shown. The upper end of the tube 58 may be closed or open.

ln order to rupture the capsule 56 and permit the material therein to flow down around and about the anchoring means 18 and into contact with the side walls of the hole 1t) surrounding the anchoring means after the mine roof bolt assembly has been inserted into the hole, a lower portion of the capsule may be provided with a tear strip 64 operable by a cord or Wire 66. The tube 58 may be cut away slightly at its lower end if necessary, as shown at 68 in Figure 4, for ease of operation of the tear strip 64 by the wire 66. In order to allow the cord or wire 66 to depend from the hole 10 for operation of the tear strip 64 after insertion of the capsule 56 and `the roof bolt assembly, the extension 62 on the connecting member 28 may have la slot 70 therein through which the cord depends, and one of the arcuate side surfaces of the nut 22 may have a longitudinal groove 72 therein aligned with the slot 70 for reception of the cord.

Accordingly, after the mine lroof bolt assembly, to-

ether with the capsule 56, has been inserted to its full extent into the drilled hole 1), and before the bolt 16 has been rotated to draw the washer 54 into tight engagement with the ceiling 12 and expand the shell 20, the cord or wire 66 is pulled to rupture the capsule, thus permitting its contents to flow downwardly into the spaces between the side Walls of the hole 10 and the anchoring means 18. In order to retain all of the material about the anchoring means 18 and to completely lill the hole llt) with the material for short distances above and below the anchoring means, the shank 46 of the bolt 16 is provided with a snugly-fitting felt or rubber washer 74 of slightly greater diameter than that of the hole 10 and spaced only slightly below the lower end of the anchoring means 18. To insure retention of the washer 74 in its proper position on the shank 46 during insertion of the assembly into the hole 10, the washer may be backed by an inexpensive sheet metal nut 75 engaged with the shank threads. Hence, all of the material will be retained about the anchoring means 18, and in this connection the capsule 56 should contain enough material to fill the hole 1) from the washer 74 to a short distance above the anchoring means 18. After the capsule 56 has been ruptured, the nut 22 is rotated to draw the washer 54 against the ceiling 12 and expand the anchoring means 18 into retaining engagement with the side walls of the hole 10, and the plastic or liquid material will set and solidify within a short time, to absolutely preclude exposure to air of the side Walls of the hole about the anchoring means and for short distances thereabove and below. At the same time, the setting of the plastic or liquid material will tend to cement the mine roof bolt assembly firmly in place in the hole 10.

As a further method of excluding air from the hole 10 to prevent possible spalling or crumbling of the side walls thereof, a large conical stopper-like washer 76, preferably of rubber or the like, is placed on the shank 46 of the bolt 16 in engagement with the head 48 thereof. This washer 76 has an undersurface shaped to fit snugly against the head 48 of the bolt 16 and also preferably is provided with a circumferential flange 78 at its base. The major diameter of the conical body of the washer 76 preferably is slightly greater than that of the hole 10, so that when the mine roof bolt assembly is completely installed, the washer acts as a stopper for the hole. Further, the washer flange 78 is compressed tightly between the washer 54 and the ceiling 12 about the hole to act as an additional seal to prevent admission of air into the hole, aside from that small quantity trapped therein by installation of the mine roof bolt assembly. In order to permit assembly of the washer 76 on the bolt 16 without disassembly of the latter from the anchoring means 18, the washer 76 may be split longitudinally.

Means other than the tear strip 64 and cord 66 shown in Figures 1 and 4 may be employed for rupturing a capsule. For example, as shown in Figures 5 and 6, the capsule 80 may have weakened portions 82 adjacent its lower ends, and the capsule-enclosing tube 84 may be somewhat shorter than the capsule, so that the latter projects outwardly from the top of the tube. In this type of capsule 80 and tube 84 construction, the hole 86 is drilled to a predetermined depth so that when the mine roof bolt assembly, together with the capsule and its enclosing tube, has been inserted almost fully into the hole, the top of the capsule 80 contacts the bottom or upper end 88 of the hole. Thereupon, a force may be exerted on the lower end of the capsule Si) and its enclosing tube 84 by the mine roof bolt assembly to cause an increase in pressure in the capsule suicient to rupture the same along its weakened portions 82, as shown in Figure 5, and permit the cementitious material to escape therefrom, The same result could be obtained by a telescoping closure (not shown) for the tube 84 over the projecting portion of the capsule 80.

The invention also contemplates other means of rupturing a capsule after the mine roof bolt assembly has been installed, as, for example, making the entire or a part (not shown) of the lower portion of a capsule of a material that is soluble in the cementitious material, so that the latter will be released within a short time, e. g., of the order of fifteen minutes, after the capsule has been filled with the cementitious material. This method of installation, of course, necessitates iilling the capsule with the material and closing and sealing the capsule immediately before use.

It thus will be seen that the objects of this invention have been fully and eectively accomplished. It will be realized, however, that various changes may be made in the specific method and apparatus shown and described for the purpose of illustrating the principles of this invention wit-hout departure from such principles. For example, the material-applying apparatus and method are usable with mine roof bolts other than the type disclosed herein. Accordingly, this invention includes all modifications of apparatus and method encompossed within the spirit and scope of the following claims.

I claim:

l. A method of installing a mine roof bolt assembly of the type including an elongated bolt and an expansible anchoring means on one end thereof in an upwardly extending hole in a mine roof which comprises: inserting a container containing a ilowable, hardenable, air-excluding material into the hole together with and ahead of the mine roof bolt assembly above the anchoring means thereof; opening the container so as to permit the material contained therein to flow out of the container by gravity; contining the material owing by gravity within the space in the hole adjacent the anchoring means of the roof bolt assembly; and expanding the anchoring means of the roof bolt assembly prior to the hardening of the material.

2. A method as dened in claim 1 wherein said container is opened by compressing the same, through upward movement of the assembly, against the upper end of the hole until ruptured.

3. A mine roof bolt installation comprising: a roof bolt assembly comprising an elongated bolt extending upwardly in a drilled hole in a mine roof, expansible anchoring means on the upper end of said bolt expanded into anchoring engagement with the wall of the hole, and means on the lower end of said bolt retained in compressive engagement with the ceiling of the mine roof about the mouth of the hole by tension in the bolt between its upper and lower ends, annular sealing means mounted on said bolt below and adjacent said expansible `anchoring means engaging the wall of the hole, a hardened water-insoluble, air-excluding material in the hole above the sealing means and substantially coextensive with the expanded anchoring means, and an opened container in `the hole above said sealing means from which the hardened material has passed.

4. Apparatus for reinforcing a mine roof against collapse comprising: a roof bolt assembly comprising an elongated bolt having expansible anchoring means on one end thereof, said assembly being insertable, anchoringmeans-end foremost, into an upwardly extending hole of a mine roof; mea-ns mounted on the other end of said bolt for compressive engagement with the ceiling of `the mine roof about the Amouth of the hole; a rupturable container containing a owable, hardenable, water-insoluble, air-excluding material for insertion into the hole by and ahead of said assembly and for rupture in the hole above said assembly permitting the material therein to flow downwardly; and annular sealing means mounted on said bolt below and adjacent said anchoring means for preventing the flow of said material in the hole downwardly below said sealing means.

5. Apparatus as dened in claim 4 wherein said means mounted on the other end of said bolt includes a gasket for sealing the mouth of the hole against entrance of air.

6. Apparatus as defined in claim 4 wherein said sealing means comprises a washer mounted on said bolt below and adjacent said anchoring means against longitudinal movement along said bolt in a direction away from said anchoring means and a gasket of flexible material slidably mounted on said bolt in engagment with the washer on the side thereof facing said anchoring means.

References Cited in the file of this patent UNITED STATES PATENTS 1,798,468 Hartzler etal. Mar. 31, 1931 2,092,341 De Vries Sept. 7, 1937 2,302,933 Barol Nov. 24, 1942 2,442,113 Bcijl May 25, 1948 2,580,414 Duley Jan. 1, 1952 2,666,354 Dim et al Jan. 19, 1954 2,667,037 Thomas et al. Jan. 26, 1954 2,682,152 Bierer June 29, 1954 2,690,879 Snyder Oct. 5, 1954 

